Which of the following would be an expected response to sympathetic (fight or flight) nervous system stimulation?

• A. Decreased heart rate
• B. Slower breathing
• C. Diminished alertness
• D. Heart rate increases

Answer: (D)

The main concept is how the body prepares for quick action during stress. When the sympathetic nervous system is stimulated, it drives the fight-or-flight response, and a hallmark of that response is raising the heart rate to boost blood flow to muscles and vital organs. This happens because adrenaline and related nerves increase the firing rate of the SA node and strengthen heart contractions, producing higher cardiac output to meet emergency needs.

So an increased heart rate is the expected response to sympathetic activation. In contrast, a slower heart rate would reflect parasympathetic effects, and slower breathing or diminished alertness would not align with the heightened arousal and vigilance produced by the sympathetic system—breathing typically becomes faster and more pronounced, and alertness increases.